Differential pressure-actuated ballcock valves are used to control the flow of water (or other liquid) from a source pipe to a user item such as a sink, urinal, or commode. Customarily they utilize a piston which carries a seal that is moved by it to open or to close a seat and thereby to control flow through the valve. The operating position of the piston is determined by whether a bias chamber at one face of the piston is vented, or is closed and contains liquid under a pressure approximating that in the source pipe.
A well-known valve of this type is manufactured by Coast Foundry and Manufacturing Company, Pomona, Calif. under the mark "Magic Float". This valve is fully described in Heyer et al U.S. Pat. No. 3,618,629, issued Nov. 9, 1971. This patent is incorporated herein by reference in its entirety for its showing of the general structure and operation of such a valve in which the improvements that are the subject matter of this invention can readily be included to its advantage.
The said Heyer patent has been a very successful product. But occasionally, after long use, especially in very dirty water, i.e., water which contains much sediment and particulates, the valve closes sluggishly, or even hangs open for an extended period of time.
Investigation has shown that at least some of these problems are caused by particulates which get underneath the seal around the piston so as to frustrate development of a sufficient differential pressure in the bias chamber (or to retard it), and the accumulation of particulates in the bias chamber.
It is an object of this invention to provide a ballcock valve without these disadvantages, and a piston to enable this result.